Hooking a sonar to a deep cycle battery

[Mr.J.]

Now that I have picked up a new sonar for the boat i would like to rig my old one up for the canoe.

I use a deep cycle batttery for the electric trolling motor to push along the canoe so I am wondering about using this same battery to run the sonar as well.

Any concerns doing this?

[Badger Shark]

I have done it before but it is probably better to have another battery so you dont run the one down faster. I just used 2 car batteries. Then again it wasnt in a canoe.

[eye-tracker]

Mr. J...

The sonar will work fine when the electric motor is not running. Once you start the electric motor you will get interference on the screen.

-sheldon

[OTRA]

Mr. J...

The sonar will work fine when the electric motor is not running. Once you start the electric motor you will get interference on the screen.

-sheldon

If you're referring to conductive noise, try putting a 100 microfrad eletrolyte capacitor along with a .1 micro across the input of the fish finder. Since its 12v any cap should handle it.

If you're referring to radiated noise, try moving the two devices further apart.

[Mr.J.]

Sheldon

On my Princecraft I have a 2nd sonar at the bow of the boat and the transducer is mounted on the troller motor. I don't reacall this ever causing any interference before.

[eye-tracker]

Mr J,

Here is the information from the Lowrance web site. Hopefully it will help, if you can live with the interference or not marking anything but bottom you will be fine with it hooked to the same battery as the electric trolling motor.

Trolling Motor Transducers
If the unit reads erratically or you get lines on the screen when the trolling motor is running, this could indicate trolling motor interference.

Trolling motor should run off of a separate power source than the electronics. Use 2 different power sources if possible.
Make sure cables are on different sides of the boat.
When using skimmer transducer on motor, use a piece of rubber under the transducer
Use ferrite blocks, one on the transducer cable, and one on power cable, Make sure to get the ferrite blocks as close as possible to the unit.
Ground the foot-control pin on the trolling motor to the negative terminal of the trolling motor battery.


-sheldon

[Mr.J.]

Sheldon

Understood.

It's sharing the same power source that may cause the interference and not the actual trolling motor.

[ady]

Interesting reply by OTRA but will a cap be able to handle it, a small cap may be rendered useless by the motor current draw. Maybe a diode isolator in-line before the cap would help - All this if you get the problem of course.....


Just thought, I have run a sonar and motor on the same cranking battery and never seen the problem and have not seen it posted here before - maybe it's a non-issue. The deep cycle battery type makes no difference to a cranker in this case.